1. Field of the Invention
The present invention relates to an image processing apparatus and an image processing method for generating a pattern using a colorless recording material, such as transparent toner or transparent ink, to form an image, and a computer-readable storage medium containing designations for causing a computer to execute the method.
2. Description of the Related Art
Printers capable of high-quality printing of a photograph taken with a digital camera have been available in recent years. Such a printer typically performs printing with toner or ink of four colors, e.g., yellow (Y), cyan (C), magenta (M), and black (K). Colorless, transparent toner is used in some cases to improve a gloss of an image or to enhance toner transferring efficiency so as to increase image quality. There are known technologies for performing printing using colorless, transparent toner.
Proposed in Japanese Patent Application Laid-open No. 2003-341186 is a technology to overcome the disadvantage associated with projection of a full-color image formed on a transparent film or a transparency through a transmission-type overhead projector (OHP). This disadvantage results from projected light that is scattered by a non-smooth portion of an image surface and contains an achromatic component. The achromatic component narrows a color reproduction range of a projected image as compared with that of a printed image, from which light is reflected to be viewed by a viewer, and also makes the projected image poor in coloration because color tone of the projected image undesirably contains gray-color components that are not contained in the original image. According to the proposed technology, in addition to color toners, transparent toner is transferred onto a transfer member to make an image surface smooth, thereby achieving high image quality.
Proposed in Japanese Patent Application Laid-open No. 2007-011028 is a technology to overcome the disadvantage in that a total toner amount is increased by a considerable amount when transparent toner is used as compared with conventional four-color printing and accordingly a large load is placed on a series of processes in electrophotographic processing. The proposed technology aims at reducing the load by performing operations as follows: a total amount of C, M, Y, and K toners is calculated; an allowable amount of the transparent toner is calculated from the total toner amount; the allowable amount is converted into a print-area ratio of the transparent toner; a masking pattern for masking a transparent-toner signal is generated using the print-area ratio of the transparent toner; and masking is performed using a designated transparent toner image and the masking pattern.
Proposed in Japanese Patent Application Laid-open No. 2007-199291 is a technology to overcome the disadvantage in that formation of a toner image on an entire surface of an image with transparent toner undesirably makes consumption of the transparent toner considerably large as compared with those of other toners, causing a developing agent for the transparent toner to degrade faster than developing agents for the other toners and, furthermore, causing running cost to increase because transparent toner is generally expensive. According to this technology, a region corresponding to a face of a person is extracted from image data and labeled as a feature region, while another region is labeled as a non-feature region. Then, a greater amount of transparent toner is applied to the feature region than the non-feature region.
Proposed in Japanese National Publication of International Patent Publication No. 2008-532066 is a technology for producing visible and tactilely detectable texture that appeals to visual sensation and tactile sensation using transparent toner, thereby to apply a transparent-toner pattern to a region where a specific color toner is applied as well as to apply a pattern across an entire surface of a sheet.
However, using the technology described in Japanese Patent Application Laid-open No. 2003-341186, it is not possible to apply a transparent-toner pattern to a specific region selected from an image. The technology described in Japanese Patent Application Laid-open No. 2007-011028 assumes that the masking pattern is a character string, such as “CONFIDENTIAL,” and a region to which a transparent-toner pattern is to be applied needs to be determined by a user. Accordingly, it is difficult to automate application of masking.
With the technology described in Japanese Patent Application Laid-open No. 2007-199291, selection is made of a region where spatial frequencies serving as a feature for regional division are low. Accordingly, this technology aims at reducing unevenness of color toners that is noticeable in low-frequency regions and adjusts only the transparent toner amount in a region-adaptive manner, but not at applying a transparent-toner pattern in a region-adaptive manner. With the technology described in Japanese National Publication of International Patent Publication No. 2008-532066, a transparent-toner pattern can be applied to a region where toner of a specific color is applied. However, this technology is less region-adaptive because this technology does not take account of a relation between an image feature of the region and the pattern to be applied thereto.
When a transparent-toner pattern is generated with transparent toner, it is necessary to specify an image region where transparent toner is to be applied and determine what pattern is to be applied. As also described in Japanese Patent Application Laid-open No. 2007-199291, an image region can be specified based on a feature of the region. However, determination as to what pattern is to be applied cannot be made in a region-adaptive manner with a known technology. With these techniques, it is difficult to improve a gloss of a specific region or providing specific unevenness to an image or to impart unique texture to the image.
Under the above circumstances, provision of an apparatus or a method that can determine a transparent-toner pattern in a region-adaptive manner has been desired; with the apparatus or the method, a gloss of a specific region in an image can be improved and specific unevenness can be provided to the image so as to impart unique texture to the image.